Ben 10 vs Hal Jordan is actually fair, not even "oh one shitstomps the other!", the matchup is just fairer than many think

with both sides having notable advantages

• Both have roughly similar Multiversal feats and scaling
• Hal would have superior combat skill and experience
• Alien X would have more traditional intelligence through Multiversal omniscience
• Feedback directly counter's a Green Lantern's weakness against energy absorbers
• Alien X has better regeneration
• Alien X is capable of resisting Hal's mind hax and time manipulation due to his extradimensional existence
• Hal could resist Alien X's mind hax
• The Omnitrix would be able to keep up with Hal
• Hal undeniably shitstomps all of Ben's aliens save for Clockwork, Feedback, and Alien X
  
• Clockwork and Alien X have greater time manipulation than Hal
• Hal has dealt with Multiversal reality warping / existence erasure before and could likely resist it

I'm just link pasting Blazer-Man's argument